It is possible that the main title of the report Marfan Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.
As Jenny points out, being able to lisp the alphabet song at age two has little to do with 'knowing' the alphabet. And, yes, most children learn the letters by sight and sound in kindergarten, although most are capable of learning this information sooner if diligently taught by parents or others.
Your baby may even begin to recognize a song or rhyme if you repeat it often. By the time she is 4 months old, your baby will show an interest in books and start to explore them by chewing or throwing them. At this age, your baby needs sturdy vinyl or cloth books that can survive chewing and are not easily torn.